1. Field of the Invention
The present invention relates to a navigation system, and more specifically to a navigation system for transmitting real time traffic information by means of a paging channel and searching for an optimal path, in real time, by means of the real time traffic information and a method for providing the traffic information.
2. Description of the Related Art
In general, positional information regarding movable bodies, such as ships, airplanes and vehicles, may be provided to navigation systems. The global positioning system (GPS) position measuring device receives radio signals representing a latitude, a longitude and an altitude, etc., from a plurality of satellites included in the GPS and calculates current positions of movable bodies. Further, the GPS position measuring device displays geographical information, including current positions, on the basis of map data stored in advance. That is, a general navigation system (GNS) provides drivers with various information, necessary for driving, by means of information received from the GPS. For instance, the GNS displays on a screen a current speed of movement, a path of movement set by a driver before driving, and an optimal path to a destination.
Core technologies of a navigation system include a positioning technology for accurately determining a position of the movable bodies and a routing technology for informing a path to a destination. The present invention addresses the latter. In general, a routing is performed by means of a digital map DB, a current position of the movable body and destination information. For the routing, algorithms, such as, a digital Dijkstra algorithm or A* algorithm are utilized.
In order to improve the precision of a routing result of such navigation system, traffic information must be included in the algorithm. Furthermore, when it is considered that the traffic information continuously changes, a continuous update for the traffic information must be performed during the travel of a vehicle.
In general, when a vehicle driver wants a routing that reflects traffic information, the vehicle driver should access a traffic information management server. For example, a connection to the traffic information management server must be performed before the vehicle driver starts toward destination, or according to the needs of a user during traveling of a vehicle, a reconnection to a traffic information management server must be performed, and a path must be received.
FIG. 1 is a block diagram of a navigation system for providing traffic information in a conventional way. In order to utilize real time traffic information during traveling, a navigation terminal 10 must be connected to a traffic server 20. The traffic server 20 obtains traffic information regarding a requested area from a traffic information database (DB) 25 and then provides it to the navigation terminal 10. However, according to this method, in order to provide real time traffic information, a connection between the navigation terminal 10 and the traffic server 20 must be performed. Accordingly, in a case in which path guidance data reflecting traffic information, from an original starting point to a destination, is received and then path guidance is performed by means of the path guidance data, a target road may not have been congested when an original path was actually calculated. However, when a vehicle moves and enters into the target road, severe congestion may have occurred due to change of traffic conditions. To avoid this situation, path guidance data including new traffic information must be received after connecting to the traffic server each time. Accordingly, a traffic information user must bear not only DB charges but also an additional communication cost of utilizing the DB.
Other technologies for transmitting traffic information by means of frequency modulation (FM) additional broadcasting have been developed. However, according to this method, since traffic information of a particular avoidance region or a wide area is transmitted, but traffic information of an area in which a user is driving at present is not transmitted, it is difficult to apply a real time optimal path search by means of traffic information updated with rapid period.
Furthermore, according to the conventional methods using the FM additional broadcasting, additional apparatus for receiving FM additional carrier must be installed. That is, in addition to a portable terminal generally used in navigation or a universal mobile communication means such as a communication module, additional hardware is necessary.
Moreover, in the navigation terminal using traffic information transmitted through the FM additional broadcasting, a real time path calculation can not be performed and only simple text messages are displayed. Accordingly, a driver must see the text messages during traveling, in order to determine and avoid congestion areas, which may be very detrimental to the driver's safety.